1. Field of the Invention
This invention relates to a new copolymer comprising units of an ester of an unsaturated aliphatic carboxylic acid and units of an ethylenically polymerizable comonomer having, in a side chain which is not part of the polymer chain, at least one amino group. This invention relates to such copolymers and their use as detergents in motor fuels, especially gasoline.
2. Discussion of the Prior Art
Numerous detergents for inclusion in fuels have heretofore been suggested. For instance, it has long been known to include in gasoline a detergent based upon an amine such as a condensation product of a secondary amine with an anhydride such as maleic anhydride. Other known detergents include materials such as polyisobutyl amines. Unfortunately, while effective, these known detergents are quite expensive, thus raising the overall price of the gasoline. It became desirable to provide a detergent which can be synthesized at substantially less cost and is similarly effective in providing detergency in the lines through which the fuels pass. It became particularly desirable to provide a detergent for gasoline which would remove deposits in the carbutetor of an automobile and, at the same time, would prevent deposit buildup on such carburetor.
Stabilized fuels have been proposed containing copolymers made from esters of unsaturated carboxylic acids. Thus, Catlin et al disclosed in U.S. Pat. No. 2,737,452, a stabilized fuel containing an oil soluble basic amino nitrogen-containing addition type polymer made from a plurality of polymerizable olefinically unsaturated compounds. One of the components is amine-free and contains 8 to 18 carbon atoms in an aliphatic hydrocarbon chain which, while in the polymer, is not part of the main polymer chain. The other component of the polymer is a comonomer which contains a basic amino nitrogen in a side chain. Such copolymer is included in a fuel oil in a small proportion, i.e., at least about 0.001 percent by weight and acts as a stabilizer therein. The copolymer of Catlin et al necessarily has units of at least 8 carbon atoms in the ester chain, for Catlin et al discloses that polymers of aminoethylmethacrylate (where the chain length is far less than 8 carbon atoms) are without effect in the formation of sediment in fuel oils even when such homopolymers contain long hydrocarbon chains.
Undoubtedly, the Catlin et al stabilizer is effective for stabilizing catalytically cracked fuel oils. It has become desirable, however, to provide a stabilizer derived from an ester of a carboxylic acid and a nitrogen containing comonomer thereof which is especially effective to remove the buildup of deposits on an engine carburetor.